The  person capable of standing back may notice that change is the one constant.  

One might do well to stand back and consider whether a perceived truth is indeed so, or whether in fact the more things apparently change, the more some things do indeed remain the same.

Following the crowd and abandoning a commitment to a long-term approach in a business you bought into believing it to be sound could lead to a real loss, especially if, six months later, it turns out that the crowd consisted of ill-informed speculating lemmings and now the shares you sold have doubled in value as sanity returned to the market.

The importance of understanding your own behaviours in relation to your actions cannot be over-stated. 

Once understood, you will be able to apply your preferred investing style consistently without emotional or psychological bias.  Something which is easier said than done.  

"An optimist will tell you the glass is half-full;
the pessimist, half-empty; and
the engineer will tell you the glass is twice the size it needs to be."